The Winchester SX4 in 20 gauge is a gas-operated semi-automatic shotgun with a 24-inch barrel and matte black finish. It uses the Active Valve gas system, which Winchester designed to cycle reliably across a wide range of shell lengths and loads without manual adjustment. 
 

Key Specifications 

• Model: SX4 
• Gauge: 20 GA 
• Action: Semi-Automatic 
• Barrel Length: 24 inches 
• Capacity: 4 rounds (2-3/4" shells) 
• Weight: 6.75 lbs. 
• Finish: Matte Black 
   

Detailed Features 

 
The Invector-Plus Flush choke system includes three chokes (Full, Modified, and Improved Cylinder), which cover the range from tight patterning for waterfowl to open patterns for upland birds or clays. The front sight is a fiber optic bead that is easy to pick up in low-light conditions. The Inflex recoil pad compresses under recoil to redirect the push downward rather than straight back, which reduces muzzle flip. The receiver is aluminum alloy; the barrel is steel with a matte black finish. 
 
At 6.75 lbs the SX4 is on the lighter end of 20-gauge semi-autos, which makes it easy to carry in the field but also means it cycles the felt recoil through a lighter platform than heavier guns. 
 

Usage Scenarios 

 
The SX4 in 20 gauge is suited for upland hunting, waterfowl hunting with 3-inch shells (the gun is 3-inch chambered), and clay target sports including skeet and trap. The 24-inch barrel is a common upland length that balances swing weight and handling in tight cover.

Owner feedback on the Winchester SX4 in 20 gauge is largely positive, with a few practical caveats.

The weight and handling get frequent mentions. At 6.75 lbs it carries easily through a full day in the field, and most owners describe the balance and swing as natural for upland or clay shooting.

Reliability is a common positive. Most owners report smooth, consistent cycling across a variety of shell types, including lighter target loads. A small number of owners note that very light or low-base shells occasionally cause a short cycle, which is common for gas-operated semi-autos set up to run heavier hunting loads.

The Inflex recoil pad is appreciated, especially by shooters moving up from a 12 gauge or those with recoil sensitivity. Felt recoil is consistently described as mild for a 20 gauge semi-auto.

The choke system and fiber optic front sight both get positive marks for being practical and functional out of the box.

Price relative to competition is the most-discussed criticism. A few owners feel the SX4 asks slightly more than comparable semi-autos from other brands at similar feature levels, though most consider the quality justifies it. Occasional comments also mention that certain aftermarket chokes do not fit the Invector-Plus thread pattern without adapters.